Several radioimmunoassays have been designed for possible detection of IgE antibodies in persons sensitive to toluene diisocyanate (TDI). Antigens were prepared by reacting o-,m- and p-tolyl isocyanates with protein. Each antigen was tested for ability to react with known anti-TDI antibodies which had been produced in guinea pigs. The ortho and para tolyl antigens demonstrated good reactivity with these antibodies. Antigens were then tested for ability to detect anti-TDI antibodies in sera from sensitized workers. Using RAST assays, reactions were noted with each tolyl antigen. Such antigens would seem to be appropriate for routine in vitro screening of workers for development of TDI sensitization. RAST assays have also been developed for detection of antibodies to hexamethylene diisocyanate (HDI) and diphenyl methane diisocyanate (MDI). Sera from sensitized workers will be evaluated for cross-reactivity with each of the isocyanate antigens. An animal model for pulmonary sensitivity to industrial chemicals is being developed. Sensitization has been achieved in guinea pigs to TDI. The model will be extended to investigate both immediate and delayed sensitivity to other industrial diisocyanates.